Synthetic apatites will be produced in the presence of strontium and fluoride combinations and studied by x-ray diffraction and acid dissolution behaviour. Acid reactivity of apatite in the presence of strontium and fluoride combinations will also be studied. Diffusion characteristics of calcium, strontium and complexing anions through protein membranes will be studied. The effect of strontium and fluoride on the production of artificial carious lesions in human enamel will be studied. Remineralization of artificial carious lesions will be studied in vitro using solution incorporating strontium and fluoride.